<html lang="en">
    <head>
        <meta charset="utf-8" />
        <title>HTML DOM - Make a draggable element</title>
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link rel="stylesheet" href="/css/demo.css" />
        <link rel="preconnect" href="https://fonts.gstatic.com" />
        <link
            rel="stylesheet"
            href="https://fonts.googleapis.com/css2?family=Inter&family=Source+Code+Pro&display=swap"
        />
        <style>
            .container {
                /* Center the content */
                align-items: center;
                display: flex;
                justify-content: center;

                /* Misc */
                min-height: 32rem;
            }
            .draggable {
                /* Required styles */
                cursor: move;
                position: absolute;
                user-select: none;

                /* Center the content */
                align-items: center;
                display: flex;
                justify-content: center;

                /* Misc */
                border: 1px solid #cbd5e0;
                height: 8rem;
                width: 8rem;
            }
        </style>
    </head>
    <body>
        <div class="container">
            <div class="draggable" id="dragMe">Drag me</div>
        </div>

        <script>
            document.addEventListener('DOMContentLoaded', function () {
                // The current position of mouse
                let x = 0;
                let y = 0;

                // Query the element
                const ele = document.getElementById('dragMe');

                // Handle the mousedown event
                // that's triggered when user drags the element
                const mouseDownHandler = function (e) {
                    // Get the current mouse position
                    x = e.clientX;
                    y = e.clientY;

                    // Attach the listeners to `document`
                    document.addEventListener('mousemove', mouseMoveHandler);
                    document.addEventListener('mouseup', mouseUpHandler);
                };

                const mouseMoveHandler = function (e) {
                    // How far the mouse has been moved
                    const dx = e.clientX - x;
                    const dy = e.clientY - y;

                    // Set the position of element
                    ele.style.top = `${ele.offsetTop + dy}px`;
                    ele.style.left = `${ele.offsetLeft + dx}px`;

                    // Reassign the position of mouse
                    x = e.clientX;
                    y = e.clientY;
                };

                const mouseUpHandler = function () {
                    // Remove the handlers of `mousemove` and `mouseup`
                    document.removeEventListener('mousemove', mouseMoveHandler);
                    document.removeEventListener('mouseup', mouseUpHandler);
                };

                ele.addEventListener('mousedown', mouseDownHandler);
            });
        </script>
    </body>
</html>
